Legendary gem. 5.2 and combat vs. assasination

So i have been really unlucky with the Spiritsever. Both on LFR and the normal raid.

However. i just recently got the fist weapon from shekzeer.

Now i have 2x dagger of the seven stars and i am running assassination for mainspec.

And for the ocational cleave fight. I use my new Claw of shek'zeer and Gara'kal OH.

My question here now. Should i just put my gem in the fist weapon and go combat next patch, Or save it and try to get a spiritsever. Wont be much more than 4 more shots at the boss max i guess.
I know you can just buy a new gem. But due to issues i will not go into details on now. I have little time to play. I more or less only raid twice a week. so i just cant get the gold. This was never a discussion about how easy it was to get gold and whatnot!!!

How does combat vs assassination look on the ptr atm. One of them way ahead ?
What should i do with my gem ?

Get a spiritsever and put the gem in it. The agility gain puts it equal or slightly above their counterparts in 5.2 for the offhand (i.e., a normal spiritsever in the offhand is as good or a bit better than a 522 offhand).

Combat, however, gains a lot more from offhand dps and the weapon will be replaced much, much quicker.

Assassination is the top single target spec right now and is actually getting a buff. Out of all classes I have seen, rogues are probably getting one of the best buffs with the increased dmg to dispatch and envenom. Look for Assassination to start to catch up to mages, locks, and windwalkers.